1. Technical Field
The invention relates to a process for hydraulically fracturing a subterranean hydrocarbon-bearing formation and more particularly to a process for fracturing the formation with a crosslinked polymer gel.
2. Background Information
The productivity or injectivity of a wellbore in fluid communication with a subterranean hydrocarbon-bearing formation may be undesirably low due to a number of causes, including low permeability of the formation rock, placement of casing cement, plugging by previously injected materials, clay damage, or produced fluid damage. Productivity or injectivity may be increased by hydraulically fracturing the formation.
Hydraulic fracturing generally entails injecting a fluid into the wellbore at a sufficient rate and pressure to overcome the tensile strength of the formation and the overburden pressure. The injected fluid creates cracks or fractures extending from the wellbore out into the formation which are usually propped open with a solid proppant entrained in the fluid. The fractures permit the flow of hydrocarbons and other fluids into or out of the wellbore.
U.S. Pat. No. 3,816,151 to Podlas, U.S. Pat. No. 3,938,594 to Rhudy et al and U.S. Pat. No. 4,137,182 to Golinkin disclose hydraulic fracturing processes using a number of crosslinked polymer solutions as fracturing fluids. The inventor has discovered that many of the crosslinking reactions prescribed by the art are very difficult to control. Uncontrolled crosslinking can occur too rapidly, producing a non-homogeneous suspension of highly viscous gel balls in a watery solution, or in the other extreme crosslinking can fail to occur at all. In either case, the result is an ineffective fracturing fluid.
A process is needed for hydraulically fracturing a subterranean hydrocarbon-bearing formation with a stable homogeneous viscous fracturing fluid having satisfactory performance properties to meet the demands of the fracture treatment.